In a small saucepan, over medium-high heat, whisk all ingredients except the coffee together until steaming hot and well combined. Pour mixture through a fine mesh strainer to remove any large pieces of pumpkin. This step is optional, but if you skip it, you will have a bit of pumpkin at the bottom of your cup.
Add coffee to a 12-ounce mug and pour in pumpkin spice mixture. Stir, top with whipped cream and a sprinkle of cinnamon if desired, and enjoy.